Assange later appeared before a magistrate's court, where he was denied bail ahead of an extradition hearing. He was remanded in custody until December 14.

The 39-year-old Australian denies the Swedish charges, and his lawyer has said the case has "political" motivations.

His lawyer, Mark Stephens, expressed disappointment, but said moves against his client and WikiLeaks would not stop the release of more secret documents.

"I am advised that WikiLeaks can continue to exist, they have a number of operatives, they have many thousands of journalists in a virtual journalistic community around the world and they will continue," Stephens said.

"We are only at cable 391 today, we will see the rest of those 250,000 cables coming out so that full information is available."

Assange has denied the sex charges, which include rape, saying they are part of a smear campaign against him.

Assange and WikiLeaks have faced increasing challenges, including hacking attacks and the closure of some bank accounts and websites, since WikiLeaks began releasing some of the tens of thousands of confidential U.S. diplomatic messages that it has obtained.

Julian Assange being taken to prison after his bail was denied.

The latest blow came even as Assange appeared in court, when Visa said it had suspended all payments to WikiLeaks, following a similar, earlier, decision by the Internet payment service PayPal.

The leaks have angered Washington, which has condemned them as illegal.

Assange's arrest was welcomed by U.S. Defense Secretary Robert Gates, who heard the news on a visit to Kabul.

A spokesman for WikiLeaks said Assange's arrest was an attack on media freedom but wouldn't stop the release of more secret documents.

They show a secret plan called "Eagle Guardian" was worked out to defend Estonia, Latvia, Lithuania, and Poland against any threat from Russian forces.

In reporting on the leaked documents, the British daily "The Guardian" notes that this is the first time since the end of the Cold War that the Western allies are known to have drawn up special military plans to defend the most vulnerable parts of Eastern Europe against a potential Russian theat.

The newspaper reports that nine NATO army divisions -- U.S., British, German, and Polish -- have been designated for combat operations in the event of any armed aggression by Russia. Naval assault forces have also been designated.

And in addition, in the case of Poland, the cables say the United States offered to deploy special naval forces to Baltic ports and to put F-16 fighter aircraft into Poland.

The cables say the military plans should be not be discussed publicly as they might lead to an "unnecessary increase" in NATO-Russia tensions. According to informed sources quoted by "The Guardian," NATO leaders endorsed the plan quietly at last month's Lisbon summit of the alliance.